Electromagnetic pulse transmitting system and method

ABSTRACT

A plasma antenna generator includes an ionizable material, an explosive charge capable of projecting the ionizable material upon detonation, and a detonator coupled with the explosive charge. An electromagnetic pulse transmitting system includes an electromagnetic pulse generator and a plasma antenna generator capable of reradiating an electromagnetic pulse emitted from the electromagnetic pulse generator. A method includes providing an explosive device comprising an ionizable material, detonating the explosive device to propel the ionizable material, and ionizing the ionizable material to form at least one plasma trail. A sensing system includes an electromagnetic pulse generator, a plasma antenna generator capable of reradiating an electromagnetic pulse emitted from the electromagnetic pulse generator, and a sensing system capable of receiving and analyzing at least a portion of the electromagnetic pulse after being reflected from an interface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for transmitting anelectromagnetic pulse. In one aspect, the invention relates to anelectromagnetic pulse generator and a plasma antenna generator capableof forming a plasma antenna for reradiating an electromagnetic pulsefrom the electromagnetic pulse generator.

2. Description of the Related Art

Electromagnetic energy can be used in many ways to sense or affectobjects from a distance. Radar, for example, is reflectedelectromagnetic energy used to determine the velocity and location of atargeted object. It is widely used in such applications as aircraft andship navigation, military reconnaissance, automobile speed checks, andweather observations. Electromagnetic energy may also be used to jam orotherwise interfere with radio frequency transmissions or to affect theradio transmitting equipment itself.

In certain situations, it may be desirable to radiate one or moreelectromagnetic pulses over an area to sense or affect objects withinthe area. Generally, as illustrated in FIG. 1, a signal generator 102generates an electromagnetic pulse, which is radiated by an antenna 104as an electromagnetic wave 106. Upon encountering an interface, such asan interface between an object 108 and the air 110, a portion of theenergy of the wave 106 is reflected as an electromagnetic wave 112. Thereflected wave 112 may then be received by a sensor 114, which analyzesthe reflected wave 112 to determine various characteristics of theobject 108.

It is often desirable to deploy such antennas, e.g., the antenna 104,during flight. For example, a spacecraft approaching a planetary bodymay deploy an antenna so that electromagnetic energy may be directedtoward the surface of the body. Conventional antennas generally includerigid or semi-rigid members that may be compactly folded for storage andtransport and then unfolded when needed. Alternatively, conventionalantennas may be wires that are explosively deployed or deployed byparachutes. A substantial amount of time is often required to deploysuch antennas, which results in additional planning to determine theappropriate time to begin deployment so that the antenna will beavailable when needed. Further, circumstances may arise in which theimmediate transmission of electromagnetic energy is desirable. If theantenna has not been deployed, there may not be sufficient time todeploy the antenna and transmit the electromagnetic energy in thedesired time frame.

It may also be desirable in certain situations to transmitelectromagnetic energy having a broad spectrum of frequencies or totransmit low frequency electromagnetic energy. Generally, longerantennas are capable of transmitting electromagnetic energy moreefficiently at lower frequencies than shorter antennas. Such longerantennas may typically be capable of transmitting electromagnetic energyhaving higher frequencies as well. Longer foldable antennas require morestorage space, may be more complex, and generally take longer to unfold.

The present invention is directed to overcoming, or at least reducing,the effects of one or more of the problems set forth above.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a plasma antenna generator isprovided. The plasma antenna generator includes an ionizable material,an explosive charge capable of projecting the ionizable material upondetonation, and a detonator coupled with the explosive charge.

In another aspect of the present invention, an electromagnetic pulsetransmitting system is provided. The electromagnetic pulse transmittingsystem includes an electromagnetic pulse generator and a plasma antennagenerator capable of reradiating an electromagnetic pulse emitted fromthe electromagnetic pulse generator.

In yet another aspect of the present invention, a method is providedincluding providing an explosive device comprising an ionizablematerial, detonating the explosive device to propel the ionizablematerial, and ionizing the ionizable material to form at least oneplasma trail.

In another aspect of the present invention, an apparatus is providedthat includes explosive means comprising an ionizable material, meansfor detonating the explosive means to propel the ionizable material, andmeans for ionizing the ionizable material to form at least one plasmatrail.

In yet another aspect of the present invention, a sensing system isprovided. The sensing system includes an electromagnetic pulsegenerator, a plasma antenna generator capable of reradiating anelectromagnetic pulse emitted from the electromagnetic pulse generator,and a sensing system capable of receiving and analyzing at least aportion of the electromagnetic pulse after being reflected from aninterface.

In another aspect of the present invention, an apparatus is providedthat includes means for emitting an electromagnetic pulse and means forpropelling an ionizable material to form at least one plasma trail forreradiating the electromagnetic pulse.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich the leftmost significant digit(s) in the reference numeralsdenote(s) the first figure in which the respective reference numeralsappear, and in which:

FIG. 1 is a stylized diagram of a conventional sensing system;

FIG. 2A is a stylized block diagram of a first illustrative embodimentof an electromagnetic pulse transmitting system according to the presentinvention;

FIG. 2B illustrates the electromagnetic pulse transmitting system ofFIG. 2A in operation;

FIG. 2C is a stylized block diagram of a second illustrative embodimentof an electromagnetic pulse transmitting system alternative to that ofFIGS. 2A and 2B according to the present invention;

FIG. 2D illustrates the electromagnetic pulse transmitting system ofFIG. 2C in operation;

FIG. 3A is a stylized diagram of an illustrative embodiment of theelectromagnetic pulse generator of FIGS. 2A-2D;

FIG. 3B is a stylized diagram of the electromagnetic pulse generator ofFIG. 3A in operation;

FIG. 4A is a stylized diagram of a third illustrative embodiment of anelectromagnetic pulse transmitting system according to the presentinvention alternative to those in FIGS. 2A-2D;

FIG. 4B is a stylized diagram of the electromagnetic pulse transmittingsystem of FIG. 4A in operation;

FIG. 5A is a stylized, partially cross-sectioned, side view of a firstillustrative embodiment of an explosive device that may be employed inthe embodiments of FIGS. 2A-2D, 4A, and 4B;

FIG. 5B is a cross-sectional view of a portion of a liner of FIG. 5Athat includes a plurality of particles of ionizable material dispersedin a matrix;

FIG. 5C is a cross-sectional view of a portion of the liner of FIG. 5Athat includes a layer of the ionizable material affixed to a basealternative to that of FIG. 5B;

FIG. 5D is a stylized diagram of the explosive device of FIG. 5A inoperation;

FIG. 6A is a partial cross-sectional, side view of a second embodimentof the explosive device of FIGS. 2A-2D, 4A, and 4B alternative to thatin FIGS. 5A-5D;

FIG. 6B is a cross-sectional view of a portion of an illustrativeembodiment of a liner of FIG. 6A having a plurality of liners disposedin openings defined by a housing;

FIG. 6C is a stylized diagram of the explosive device of FIG. 6A inoperation;

FIG. 6D is a stylized diagram of a generally hollow, conical pattern ofplasma trails that may be formed by the explosive device of FIG. 6A;

FIG. 7A is a side view of a third illustrative embodiment of theexplosive device of FIGS. 2A-2D, 4A, and 4B alternative to embodimentsof FIGS. 5A-5D and FIGS. 6A-6D;

FIG. 7B is a bottom, plan view of the explosive device of FIG. 7A;

FIG. 7C is a cross-sectional view of the explosive device of FIGS. 7Aand 7B taken along the line 7C-7C of FIG. 7B;

FIG. 7D is a partial cross-sectional, side view of an explosively formedprojectile device of FIG. 7C;

FIG. 8A is a side view of a fourth illustrative embodiment of theexplosive device of FIGS. 2A-2D, 4A, and 4B alternative to theembodiments of FIGS. 5A-5D, FIGS. 6A-6D, and FIGS. 7A-7D;

FIG. 8B is a cross-sectional view of the explosive device of FIG. 8Ataken along the line 8B-8B in FIG. 8A;

FIG. 8C is a stylized diagram of the explosive device of FIG. 8A inoperation;

FIG. 9A is a stylized diagram of an illustrative embodiment of a sensingsystem according to the present invention; and

FIG. 9B is a stylized diagram of the sensing system of FIG. 9A inoperation.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a developmenteffort, even if complex and time-consuming, would be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

A first embodiment of an electromagnetic pulse transmitting systemaccording to the present invention is shown in FIGS. 2A and 2B.Referring to FIG. 2A, an electromagnetic pulse transmitting system 200includes a plasma antenna generator 202 and an electromagnetic pulsegenerator 204. The plasma antenna generator 202 includes an explosivedevice 206 and a detonator 208 attached thereto for detonating theexplosive device 206. A power source 210 is attached to the detonator208 via a switch 212 that, when closed, provides a path for power fromthe power source 210 to fire the detonator 208 and detonate theexplosive device 206. While a common throw-type switch is shown in FIG.2 as the switch 212, the invention is not so limited. The switch 212 maybe any switch known to the art.

The explosive device 206 includes an explosive charge (not shown), madeof HMX (cyclotetramethylenetetranitramine), an HMX blend, RDX(cyclotrimethylenetrinitramine), an RDX blend, LX-14 (an HMX/estaneblend), or the like. However, other suitable explosive materials may beemployed. The explosive device 206 also includes an ionizable materialthat may be arranged in various configurations as will be more fullydescribed below. Upon detonating the explosive device 206, as shown inFIG. 2B and represented by a graphic 213, particles 214 of the ionizablematerial are propelled by the explosive force through the air, in anychosen, random, or chance direction, and are aerodynamically heated.Only one of the particles 214 is shown in FIG. 2B for clarity. Theparticles 214 may be, for example, atoms, molecules, pieces, and/orslugs of the ionizable material.

As the particles 214 are heated by friction with the air as a result ofthe detonation, the ionizable material is ionized, producing plasmatrails 216 (only one shown for clarity) of ions and free electrons. Thefree electrons act as an antenna, reradiating the electromagnetic pulse218 from the electromagnetic pulse generator 204 having frequencies thatare below the plasma cut-off frequency of the trail 216. Generally,electromagnetic pulses having frequencies that are equal to or greaterthan the plasma cut-off frequency propagate through the plasma.Electromagnetic pulses having frequencies that are below the plasmacut-off frequency are reflected by the plasma. The plasma cut-offfrequency is generally proportional to the square root of the electrondensity of the plasma. Further, the plasma trails 216 may generally belonger than conventional antennas, thereby allowing electromagneticpulses having lower frequencies (i.e., longer wavelengths) to bereradiated as compared to conventional antennas.

While the electromagnetic pulse transmitting system 200 illustrated inFIGS. 2A and 2B includes only one explosive device 206, the presentinvention is not so limited and may include any number of explosivedevices 206. For example, in a second embodiment, an electromagneticpulse transmitting system 220, as shown in FIG. 2C, comprises a plasmaantenna generator 222 that includes two explosive devices 206. Upondetonating the explosive devices 206, particles 214 are propelled indifferent directions, as shown in FIG. 2D. The resulting plasma trails216 form a dipole-like antenna for reradiating the electromagnetic pulseemitted from the electromagnetic pulse generator 204. Any of theexplosive devices 206, if more than one is present, may be configured topropel the particles in any chosen, random, or chance direction withrespect to any of the other explosive devices 206.

The ionizable material (not shown in FIGS. 2A and 2B) may be made fromany material capable of being ionized as a result of aerodynamic heatinginduced by being propelled by the explosive charge. For example, theionizable material may be made of one or more alkali metals, may be madeof a compound of one or more alkali metals, such as alkali salts, alkalicarbonates, and the like, or may be a constituent of a compound of oneor more alkali metals. Alkali metals include lithium, sodium, potassium,rubidium, cesium, and francium. Further, the ionizable material may bemechanically combined with another material. For example, the ionizablematerial may comprise particulates within another material or maycomprise a layer affixed to another material. The ionizable material maybe a component of a clathrate, in which particles of the ionizablematerial may be trapped within the crystal lattice of another material.The ionizable material may be a component of an intercalation compound,wherein particles of the ionizable material may be trapped betweenlayers of another material's crystal lattice.

The electromagnetic pulse generator 204 may be any type of generatorknown to the art capable of generating an electromagnetic pulse. Forexample, as illustrated in FIG. 3A, the electromagnetic pulse generator204 may be a radio frequency energy generator 302 electrically coupledwith an explosive flux compressor 304. The explosive flux compressor 304includes a metallic tube 306 (or “armature”) containing a high explosivematerial, such as HMX, an HMX blend, RDX, an RDX blend, or LX-14. Thehigh explosive material in the tube 306 may be of the same material asthe explosive device 206 (shown in FIGS. 2A-2B), but this is notnecessary to the practice of the invention. The tube 306 is disposedwithin a metallic coil 308 (or “stator”). The radio frequency energygenerator 302 generates a current that flows through the tube 306 andthe coil 308 that generates a magnetic field therebetween.

Upon detonating the explosive material within the tube 306, as shown inFIG. 3B and represented by a graphic 309, the resulting blast flares thetube 308, which then contacts the coil 308. The resulting short circuitdiverts the current, and the magnetic field produced by the current,into the undisturbed coil 308 ahead of the progressing blast. As theexplosive front advances, the magnetic field is compressed into asmaller volume, which creates a substantial rise in the current flowingthrough the coil 308 ahead of the blast. Once the explosive front hasprogressed through the tube 306, the electromagnetic pulse flowingthrough the coil 308 is transmitted (as indicated by an arrow 310) tothe plasma trail 218 and is thus reradiated.

FIGS. 4A and 4B illustrate, in a third embodiment, an electromagneticpulse transmitting system 400, in which the explosive flux compressor304 (shown in FIGS. 3A and 3B) and the explosive device 206 (shown inFIGS. 2A and 2B) are combined into a single device. Referring now toFIG. 4A, the electromagnetic pulse transmitting system 400 includes anexplosive device 402 and a detonator 404 attached thereto for detonatingthe explosive device 402. A power source 406 is attached to thedetonator 404 via a switch 408 that, when closed, provides a path forpower from the power source 406 to fire the detonator 404 and detonatethe explosive device 402. As in the first embodiment, the switch 408 maybe any switch known to the art. Further, the explosive device 402includes an explosive charge, made of HMX, an HMX blend, RDX, an RDXblend, LX-14, or the like, and an ionizable material that may bearranged in various configurations as will be more fully describedbelow.

Still referring to FIG. 4A, the explosive device 402, which includes ametallic tube 414 like the tube 306 of FIGS. 3A and 3B, is disposedwithin a metallic coil 410. A radio frequency energy generator 412generates a current that flows through the tube 414 and the coil 410,thus generating a magnetic field therebetween. Upon detonation of theexplosive device 402, as shown in FIG. 4B and represented by a graphic415, the combination of the tube 414 and the coil 410 act as a explosiveflux compressor, like the explosive flux compressor 304 of FIGS. 3A and3B. Further, particles 416 (only one shown for clarity) of the ionizablematerial are expelled by the explosive blast from the detonatedexplosive device 402 to create a plasma trail 418. The electromagneticpulse released from the coil 410 is transmitted (as indicated by anarrow 420) to the plasma trail 418 and is thus reradiated.

As indicated above, the explosive device 206, 402 may take manydifferent forms. FIG. 5A illustrates a first embodiment of the explosivedevice 206, 402 according to the present invention. In the illustratedembodiment, the explosive device 206, 402 is a shaped charge device 502.Generally, shaped charge devices employ explosive products, created bydetonating a highly explosive material, to create great pressures thataccelerate a liner and form a very high-speed metal jet. In theillustrated embodiment, the shaped charge device 502 comprises anexplosive charge 504 partially encased by a casing 506. The explosivecharge 504 may be made of any explosive material known in the art havinga high detonation velocity and/or high brisance, e.g., materialscontaining HMX, an HMX blend, RDX, an RDX blend, LX-14, or the like.Generally, a high detonation velocity explosive is characterized as thathaving a detonation velocity of at least about 6000 meters per second.

Still referring to FIG. 5A, a forward face 508 of the explosive charge504, in the illustrated embodiment, is generally V-shaped incross-section; however, the invention is not so limited. Rather, theforward face 508, and a liner 510 affixed to the forward face 508, mayhave any cross-sectional shape known to the art. The liner 510 comprisesthe ionizable material, as defined above, and any desired materialappropriate for shaped charge liners. In various embodiments, the liner508 may be made of the ionizable material and copper or a copper alloy.

As illustrated in FIG. 5B, the liner 510 may include particles 512 ofthe ionizable material (only one indicated) in a matrix 514 of copper, acopper alloy, or any other shaped charge liner material. Alternatively,as shown in FIG. 5C, the liner 510 may include a layer 516 of theionizable material affixed to a base 518 of copper, a copper alloy, orany other shaped charge liner material. The invention, however,encompasses any arrangement or configuration of ionizable material andshaped charge liner material for the liner 510.

Referring now to FIG. 5D, upon detonation of the explosive charge 504(represented by a graphic 516) by the detonator 208, 404, the liner 510collapses inwardly and is projected forward as a jet 520 comprising theshaped charge liner material (e.g., the matrix 514 or the base 518) andthe ionizable material (e.g., the particles 512 or portions of the layer516). The plasma trails 216, 418 (as shown in FIGS. 2B and 4B,respectively) of ions and free electrons are generated as the ionizablematerial within the jet 520 is propelled through the air. Thus, the jet520, which contains the plasma trails 216 418, may be used to reradiatethe electromagnetic pulse 218 radiated from the signal generator 204(illustrated in FIG. 2B) or to reradiate the electromagnetic pulse 420from the coil 410 (illustrated in FIG. 4B).

Referring now to FIG. 6A, a second embodiment of the explosive device206, 402 according to the present invention is shown. In the illustratedembodiment, the explosive device 206, 402 is an explosively formedprojectile device 602. Generally, explosively formed projectile devicesemploy explosive products, created by detonating a highly explosivematerial, to create great pressures that accelerate a liner whilesimultaneously reshaping it into a rod or some other chosen shape.

In the illustrated embodiment, the explosively formed projectile device602 comprises an explosive charge 604 partially encased by a casing 606.The explosive charge 604 may be made of any explosive material known inthe art having a high detonation velocity and/or high brisance, asdiscussed above. The explosively formed projectile device 602 furtherincludes a liner 608 affixed to a forward face 610 of the explosivecharge 604. Both the forward face 610 and the liner 608 affixed theretomay have any desired shape. The liner 608 comprises the ionizablematerial, as defined above, and any material known to the art as beingsuitable for explosively formed projectile device liners. As in thefirst embodiment of the explosive device 206, 404, the liner 608 may bemade of the ionizable material and copper or a copper alloy. Further,the liner 608 may have a construction such as that shown in FIGS. 5B and5C.

Alternatively, as illustrated in FIG. 6B, the single liner 608 may bereplaced by a plurality of liners 612 held within openings 614 definedby a housing 616. The liners 612 comprise the ionizable material, asdefined above. While the liners 612 shown in FIG. 6B are concavelyshaped, the invention encompasses liners 612 having any chosen shape.

When the explosive charge 604 is detonated by the detonator 208, 404,the liners 612 are propelled by the resulting explosive force, as shownin FIG. 6C. Each of the liners 612 produces a plasma trail 618 (only oneindicated) that can be used to reradiate the electromagnetic pulseemitted from the electromagnetic pulse generator 204 (as illustrated inFIG. 2B) or to reradiate the electromagnetic pulse emitted from the coil410 (as illustrated in FIG. 4B).

In the embodiment illustrated in FIG. 6B, the liners 612 are arrangedsuch that a central portion 620 of the housing 616 contains no slugs616. As shown in FIG. 6D, such a configuration is designed to produce ahollow, conical pattern 622 of plasma trails 618 (only one shown). Thepresent invention, however, encompasses any chosen configuration ofliners 612 to produce a desired pattern of plasma trails 618.

FIGS. 7A-7D illustrate a third embodiment of the explosive device 206,402 according to the present invention comprising a multiple explosivelyformed projectile device 702. Referring to FIGS. 7A-7C, a housing 704contains a plurality of explosively formed projectile devices 706 heldin a chosen configuration. Each of the devices 706 comprises anexplosive charge 708 partially encased by a casing 710, as shown in FIG.7D. The explosive charge 708 may be made of any explosive material knownin the art having a high detonation velocity and/or high brisance, asdiscussed above. Each of the devices 706 further includes a liner 712affixed to a forward face 714 of the explosive charge 708. Both theforward face 714 and the liner 712 affixed thereto may have any desiredshape. The liner 712 comprises the ionizable material, as defined above,and any material known to the art as being suitable for explosivelyformed projectile device liners. As in the first embodiment of theexplosive device 206, 404, the liner 712 may be made of the ionizablematerial and copper or a copper alloy. Further, the liner 712 may have aconstruction such as that shown in FIGS. 5B and 5C.

When each of the explosive charges 708 is detonated by the detonators716, the liners 712 are propelled by the resulting explosive force inthe same fashion as the second embodiment, as shown in FIG. 6C. Each ofthe liners 712 produces a plasma trail 618 (only one indicated in FIG.6C) that can be used to reradiate the electromagnetic pulse emitted fromthe electromagnetic pulse generator 204 (as illustrated in FIG. 2B) orto reradiate the electromagnetic pulse emitted from the coil 410 (asillustrated in FIG. 4B).

In the embodiment illustrated in FIGS. 7A-7C, the devices 706 arearranged to produce a hollow, conical pattern similar to the conicalpattern 622 of plasma trails 618 (only one shown) produced by the secondembodiment, as shown in FIG. 6D. The present invention, however,encompasses any chosen configuration of liners 712 to produce a chosenpattern of plasma trails 618. For example, various devices 706 held bythe housing 704 may have differing configurations of the liners 712.

FIGS. 8A and 8B illustrate a fourth embodiment of the explosive device206, 402 according to the present invention comprising a radialexplosively formed projectile device 802. The device 802 comprises anexplosive charge 804 partially encased by a casing 806. The explosivecharge 804 may be made of any explosive material known in the art havinga high detonation velocity and/or high brisance, as discussed above. Thecasing 806 defines a plurality of openings 808 in which are disposed acorresponding plurality of liners 810. The liners 810 comprise theionizable material, as defined above, and any material known to the artas being suitable for explosively formed projectile device liners. Forexample, the liners 810 may be made of the ionizable material and copperor a copper alloy. Further, the liners 810 may have a construction suchas that shown in FIGS. 5B or 5C. While the liners 810 shown in FIG. 8Bare concavely shaped, the invention encompasses liners 810 having anychosen shape.

When the explosive charge 804 is detonated (represented by a graphic811) by the detonator 208, 404, the liners 810 are propelled by theresulting explosive force, as shown in FIG. 8C. Each of the liners 810produces a plasma trail 812 (only one indicated) that can be used toreradiate the electromagnetic pulse emitted from the electromagneticpulse generator 204 (as illustrated in FIG. 2B) or to reradiate theelectromagnetic pulse emitted from the coil 410 (as illustrated in FIG.4B).

In certain situations, it may be desirable to radiate one or moreelectromagnetic pulses over an area to sense or affect objects withinthe area and to sense structures, such as caves, bunkers, shelters,caverns and pools underground within the area. FIG. 9A illustrates anembodiment of a sensing system 900 including the electromagnetic pulsetransmitting system 220, first shown in FIGS. 2A-2B, and sensors 910,911. However, any electromagnetic pulse transmitting system as describedherein may be used. In the illustrated embodiment, the electromagneticpulse transmitting system 220 is located over an area 902. A truck 904,an underground pool 906, and a cavern 908 are located within the area902. The sensors 910, 911 are shown above the area; however, they mayalternatively be located within the area 902 or in any chosen location,as will be more fully described later. There also may be any chosennumber of sensors 910, 911 and they may be of similar or differentconfigurations to make various analyses as known to the art.

Referring now to FIG. 9B, the electromagnetic pulse transmitting system220 is activated, as described above, to radiate electromagnetic pulses912, 914, 916, 918 toward the area 902. In the illustrated embodiment,at least a portion of the electromagnetic pulse 912 is reflected by aninterface between the truck 904 and air 920 and is then received by thesensor 910. At least a portion of the electromagnetic pulse 914 isreflected by an interface between the pool 906 and the surroundingground 922 and is then received by the sensor 910. Similarly, at least aportion of the electromagnetic pulse 916 is reflected by an interfacebetween an article 924 (or some other article) within the cavern 908 andthe air 920 within the cavern and is then received by the sensor 911.Further, at least a portion of the electromagnetic pulse 918 isreflected by an interface between the ground 922 defining the cavern 908and the air 920 within the cavern 908 and is then received by the sensor911. Each of the sensors 910, 911 may be placed in any chosen locationsuch that it is capable of receiving the desired electromagnetic pulses912, 914, 916, 918.

This concludes the detailed description. The particular embodimentsdisclosed above are illustrative only, as the invention may be modifiedand practiced in different but equivalent manners apparent to thoseskilled in the art having the benefit of the teachings herein.Furthermore, no limitations are intended to the details of constructionor design herein shown, other than as described in the claims below. Itis therefore evident that the particular embodiments disclosed above maybe altered or modified and all such variations are considered within thescope and spirit of the invention. Accordingly, the protection soughtherein is as set forth in the claims below.

1-15. (canceled)
 16. An electromagnetic pulse transmitting system,comprising: an electromagnetic pulse generator; and a plasma antennagenerator capable of reradiating an electromagnetic pulse emitted fromthe electromagnetic pulse generator.
 17. An electromagnetic pulsetransmitting system, according to claim 16, wherein the electromagneticpulse generator further comprises: a radio frequency energy generator;and an explosive flux compressor, electrically coupled with the radiofrequency energy generator, for compressing energy generated by theradio frequency energy generator and producing the electromagneticpulse.
 18. An electromagnetic pulse transmitting system, according toclaim 17, wherein the explosive flux compressor further comprises: acoil electrically coupled with the radio frequency energy generator; atube electrically coupled with the radio frequency energy generator anddisposed within the coil; an explosive charge disposed within the tube;and a detonator for detonating the explosive charge.
 19. Anelectromagnetic pulse transmitting system, according to claim 17,wherein the explosive flux compressor comprises the plasma antennagenerator.
 20. An electromagnetic pulse transmitting system, accordingto claim 16, wherein the plasma antenna generator further comprises: anexplosive device comprising an ionizable material and capable ofprojecting the ionizable material therefrom upon detonation; and atleast one detonator coupled with the explosive device.
 21. Anelectromagnetic pulse transmitting system, according to claim 20,wherein the ionizable material comprises an alkali metal, a compound ofthe alkali metal, a constituent of the compound of the alkali metal, aclathrate of the alkali metal, a constituent of the clathrate of thealkali metal, an intercalation compound of the alkali metal, or aconstituent of the intercalation compound of the alkali metal.
 22. Anelectromagnetic pulse transmitting system, according to claim 20,wherein the ionizable material comprises a material selected from thegroup consisting of an alkali metal, an compound of an alkali metal, aconstituent of the compound of the alkali metal, a clathrate of analkali metal, a constituent of the clathrate of the alkali metal, anintercalation compound of an alkali metal, and a constituent of theintercalation compound of the alkali metal.
 23. An electromagnetic pulsetransmitting system, according to claim 20, wherein the explosive devicefurther comprises: a casing defining a cavity therein; an explosivecharge disposed with the cavity and having a forward face; and a linercomprising the ionizing material affixed to the forward face of theexplosive charge.
 24. An electromagnetic pulse transmitting system,according to claim 23, wherein the liner further comprises a pluralityof particles of the ionizing material dispersed in a matrix.
 25. Anelectromagnetic pulse transmitting system, according to claim 23,wherein the liner further comprises a base and a layer of the ionizingmaterial affixed thereto.
 26. An electromagnetic pulse transmittingsystem, according to claim 20, wherein the explosive device furthercomprises a shaped charge device.
 27. An electromagnetic pulsetransmitting system, according to claim 20, wherein the explosive devicefurther comprises an explosively formed projectile device.
 28. Anelectromagnetic pulse transmitting system, according to claim 20,wherein the explosive device further comprises: a housing defining aplurality of openings therein; and a plurality of shaped charge devicesor a plurality of explosively formed devices received in the openings.29. An electromagnetic pulse transmitting system, according to claim 28,wherein the plurality of openings are defined by the housing such thatthe plurality of shaped charge devices or the plurality of explosivelyformed devices are capable of producing a generally hollow, conicalpattern of plasma trails upon their detonation.
 30. An electromagneticpulse transmitting system, according to claim 20, wherein the explosivedevice further comprises: a casing defining a cavity therein; anexplosive charge disposed with the cavity and having a forward face; anda housing defining a plurality of openings therethrough and affixed tothe forward face of the explosive charge; and a plurality of linerscomprising the ionizable material received in the plurality of openings.31. An electromagnetic pulse transmitting system, according to claim 30,wherein the plurality of openings are defined by the housing such thatthe plurality of liners are capable of producing a generally hollow,conical pattern of plasma trails upon detonation of the explosivecharge.
 32. An electromagnetic pulse transmitting system, according toclaim 20, wherein the explosive device further comprises: a casingdefining a cavity therein and a plurality of openings therethrough; anexplosive charge disposed with the cavity; and a plurality of linerscomprising the ionizable material received in the plurality of openings.33-45. (canceled)
 46. An apparatus, comprising: means for emitting anelectromagnetic pulse; and means for propelling an ionizable material toform at least one plasma trail for reradiating the electromagneticpulse.
 47. An apparatus, according to claim 46, wherein the means foremitting an electromagnetic pulse comprises an electromagnetic pulsegenerator.
 48. An apparatus, according to claim 46, wherein the meansfor propelling comprises a plasma antenna generator. 49-50. (canceled)